I'm hoping to mesh my power supply and change the fan but before doing it if there is anything I should not touch in the power supply, I'm pretty sure it can hold a charge for several days after being used in the capacitators and I dont want to be fried.

So, has anyone got any tips and techniques on psu modding they could share with me?

Should not hold a charge for days, maybe an hour or 2 MAX. Unplug from the wall and try turning the computer on a few times to make sure it releases the power stored and then let it sit fro a couple hours and I do not think you will have a problem as long as you don't go trying to mod the actual components and stick to just the case!